Over the course of an operating cycle of a gas turbine engine, a compressor section of the engine may experience compressor stall. Compressor stall is a limiting factor in the operation of gas turbine engines. In modern gas turbine engines, unstable flow may develop in the compressor during acceleration phases and/or under high altitude and lower speed flight conditions. Such unstable flow may lead to stall, which may increase turbine temperature and mechanical vibration along with simultaneously reducing the cooling air supplied to the turbine. Stall may lead to turbine failure if the compressor stall is not recognized and corrective action is not taken.
During transient engine operation (e.g., during engine acceleration or deceleration), the compressor operating line may shift significantly with respect to steady-state conditions. For example, the flow admitted by the turbine as a function of pressure may be significantly reduced as fuel flow is increased during an engine acceleration transient, thereby substantially changing the compressor operating line. In addition, other transient effects such as heat transfer, tip clearance, and variable geometry and bleed control may result in large variations in the overall compressor operating line. Such variations may in turn, affect individual compressor stage operating conditions and a margin to aerodynamic instability.
Monitoring engine characteristics directly or indirectly may be an effective means for monitoring and controlling stall margin in a gas turbine engine. The thermal characteristics of the engine, including the compressor section, can be synthesized or calculated using sensed parameters. Further, thermal characteristics may be estimated by linear or non-linear models of engine components and their characteristics. Such characteristics may provide information used to determine an acceptable level of stall margin. Such parameters may be monitored and/or controlled using a control system having a variety of hardware and/or software control elements.
Modern aircrafts employing gas turbine engines require fast response and better transient performances under compressor stall requirements at all flight conditions. Thusly, a need exists for a control system that controls stall margin of a gas turbine engine in real time and overcomes computational inefficiencies of prior control system designs.